Our ultimate goal is to develop a new and simple method to microencapsulate drugs and other bioactive substances, particularly biomacromolecules such as proteins and peptides, in biodegradable controlled-release polymers. Current methods of microencapsulation in polymers such as poly(lactic-co-glycolic acid) (PLGA) suffer from: a) protein instability including use of protein-denaturing organic solvents, b) expensive large-scale, aseptic processing for encapsulation of each peptide/protein of interest, and c) the inability of clinicians at the point-of-care or other non formulation scientists in the field to effectively perform encapsulation. We will exploit our novel finding of spontaneous PLGA pore closing to microencapsulate proteins and peptides by: creating polymer delivery systems with defined pore networks, placing the polymers in the presence of an aqueous drug solution of interest, and then causing the pore network to close, e.g., by simple heating to physiological temperature. Unlike the vast majority of microencapsulation methodologies, which place drug in contact with dissolved polymer before or during microencapsulation, this approach creates a new paradigm in microencapsulation, whereby the biomaterial system is initially created and then microencapsulation is performed at the very end of preparation. In a sense, the polymer pore network microencapsulates by "itself" spontaneously-hence the term, "self-microencapsulation." Moreover, microencapsulation a) takes place under nondenaturing conditions without the need for organic solvent, b) could be done inexpensively with terminally sterilized porous PLGA microspheres for multiple peptides and/or proteins, c) would be applicable to numerous polymer configurations and geometries such as microspheres, nanospheres, tissue engineering scaffolds, drug-eluting stents, and d) could be performed by clinicians and investigators in the field, since encapsulation is by simple aseptic mixing of protein and polymer. This proposal will test the hypothesis that PLGA microspheres entrapping high loading of protein or peptide drugs can be prepared reproducibly by self-microencapsulation, and the resulting polymer will exhibit excellent drug stability and release performance both in vitro and in vivo. This hypothesis will be tested in 3 specific aims: 1) determine the effect of formulation variables on self- microencapsulation of model proteins, 2) investigate the mechanism of spontaneous pore closing in aqueous media, and 3) test the feasibility of self-encapsulation to stabilize and control the release of therapeutic peptides and proteins in vitro and in vivo. PUBLIC HEALTH RELEVANCE: This project tests the feasibility of a brand new method of microencapsulation based on a recent finding from our group demonstrating how biodegradable polymers can heal their tiny holes and cracks spontaneously in water. The microencapsulation method does not use organic solvents and could have far reaching applications to the slow delivery of the important biomacromolecular class of drugs and vaccine antigens from injectable depots, tissue engineering scaffolds, and drug-eluting stents.